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Cyclical Mill Vibration & Power Discussion
- Thread starter PeterT
- Start date
The 935 has 2 belts. The larger variable speed belt & smaller motor drive belt. Both were checked visually & confirmed as new condition - no cracks, no edge wear, laid perfectly flat on table, minimal dust in the head. Not sure if a linked belt would apply in this case, I could inquire.
The drive belt was replaced because a) it was in stock at time of rebuild b) I was concerned it was riding a bit low on the stepped pulley possibly indicating it was stretched or slightly large from factory & might be contributing to a belt resonance 'flap'. I've since learned this vertical belt position is 'normal' or at least not deemed problematic. With the head off its more obvious there is running gap between the belt 7 casting so no clearance issue.
Now the variable speed drive belt, only in hindsight, I wish I replaced. But that's only rearview mirror assessment because there is still a hint of background resonant noise once all assembled again. But the machine is significantly quieter than when the slightly loose-ish bearing was replaced in gear shaft assembly = the prime suspect at the time. Had the noise been 100% removed instead of 90% removed, then the vari-speed belt would not have been required. I've been told that even though belts can look good & measure good, they can still have 'something' amiss that can cause a harmonic, be it composition or Monday morning rubber batch? I dunno. So that may well be the next step if this noise slowly reverts to worsening over time. That's the rather frustrating chicken & egg thing, maybe the shaft bearing was the effect of the belt vs the other way around. I do recognize the noise is on my OCD radar so one opportunity mentioned to me is another member has the same machine, I'll be listening to it soon just to compare. That wont help my machine specifically but at least will give me baseline expectation of what 'normal' sounds like again.
The drive belt was replaced because a) it was in stock at time of rebuild b) I was concerned it was riding a bit low on the stepped pulley possibly indicating it was stretched or slightly large from factory & might be contributing to a belt resonance 'flap'. I've since learned this vertical belt position is 'normal' or at least not deemed problematic. With the head off its more obvious there is running gap between the belt 7 casting so no clearance issue.
Now the variable speed drive belt, only in hindsight, I wish I replaced. But that's only rearview mirror assessment because there is still a hint of background resonant noise once all assembled again. But the machine is significantly quieter than when the slightly loose-ish bearing was replaced in gear shaft assembly = the prime suspect at the time. Had the noise been 100% removed instead of 90% removed, then the vari-speed belt would not have been required. I've been told that even though belts can look good & measure good, they can still have 'something' amiss that can cause a harmonic, be it composition or Monday morning rubber batch? I dunno. So that may well be the next step if this noise slowly reverts to worsening over time. That's the rather frustrating chicken & egg thing, maybe the shaft bearing was the effect of the belt vs the other way around. I do recognize the noise is on my OCD radar so one opportunity mentioned to me is another member has the same machine, I'll be listening to it soon just to compare. That wont help my machine specifically but at least will give me baseline expectation of what 'normal' sounds like again.
